Apparatus for the heat-treatment of solid material



M. LINTZ 2,521,588

APPARATUS FOR THE HEAT-TREATMENT OF SOLID MATERIAL Sept. 5, 1950 3 Sheets-Sheet 1 Filed July 15, 1946 INVENTOR- Ma/"k Lin 2; ala/l- Sept. 5, 1950 M. LINTZ 2,521,588

I APPARATUS F OR THE HEAT-TREATMENT OF SOLID MATERIAL Filed July. 15, 1946 3 Sheets-Sheet 2 )NVENTOR Mark L/m ATTORN EY M. LINTZ Sept. 5, 1950 APPARATUS FOR THE HEAT-TREATMENT OF SOLID MATERIAL 3 Sheets-Sheet 5 Filed July 15, 1946 INVEJIQTOR Mark 1.1/173 I ATTORNEY m mm-H lwi uw Patented Sept. 5, 1950 TENT OFFICE APPARATUS FOR THE HEAT-TREATMENT F SOLID MATERIAL Mark Lintz, San Francisco, Galif.

Application July 15, 1946, Serial No. 683,660

3 Claims. 1

This invention relates to a process and an improved apparatus for the heating of granular solids.

In the heating of solid materials toeffect a calcination or roasting, the solids are introduced into one end of a rotary kiln, oil, powdered coal or gas being burned as a fuel at the other end of the kiln so that the flame and products of combustion pass counter-current to the granular solids which advance through the kiln. In many operations, it is customary to discharge the products of combustion directly to the atmosphere from the solid inlet end of the kiln and to introduce the cold solid material to be heated directly into the kiln. Unless the kiln is made of relatively great length, the exit gas temperature to the atmosphere will be relatively high and considerable heat loss will follow. To ensure heating of the solid to the desired temperature, a high flame temperature must be employed.

In an attempt to avoid these disdavantages', e. g., the heat loss and high fiame temperature, it has previously been proposed to pass the products of combustion from the kiln through the solids as they passed over a series of baffles. This arrangement is satisfactory so long as the granular solid is relatively coarse and of substantially the same size so that the back pressure or resistance to flow of the hot gas is not too great.

With. a finely divided material or one which is not uniform, the resistance to flow of the hot gases is too great.

In accordance with the present invention, I provide an apparatus arrangement and a process in which a maximum of heat economy is effected to the end that maximum utilization is ensured of the heat available from the fuel burned. In accordance with this invention, for example, I provide a system or apparatus arranged in which the heated product issuing from the kiln or furnace is passed counter-current to the air stream introduced into the kiln or furance so that the incoming air is heated before admission to the combustion zone. The products of combustion from the kiln or furnace are withdrawn and passed counter-current to and in direct heat exchange with the incoming stream of granular solids. In this way, the solid materials are heated and brought u to a temperature suitable for introduction of the material into the kiln so that maximum fuel utilization is secured and so that a kiln of only moderate length need be employed. The preheater construction utilized comprises a series of baffles arranged in such a manner that the granular materials cascade over the bailies 2 which are heated by a hot gas passed in direct contact with the baffles and with the granular materials. In this way, the over-all heat econoiny of the operation is vastly improved.

For example, in one installation operated on limestone, the rotary kiln employed was of such a length and the rate of the through-put of the limestone undergoing calcination was such that the gas temperature issuing from the kiln was 12G0-1500 F. This gas was introduced into a preheater, the construction of which will be further explained in detail. The stone issuing from the preheater into the kiln was at a temperature of il-1200 F. while the temperature of the gas issuing from the preheater to the atmosphere was about 360 F. Prior to installation of the preheater, the gas issuing from the kiln was permitted to pass directly to the atmosphere. This gas temperature provided a large heat loss which was materially reduced by utilizing the system I have broadly outlined. In addition, the over-all throughput of the calcining kiln operation was increased substantially as compared to the through-put prior to the installation of the prehe'ater while the fuel utilization per ton of calcined solid was materially reduced.

It is in general the broad object of the present invention to provide an improvement in the heating of granular solids to the end that the overall heat economy of the operation is improved.

A further object of the present invention is to provide an improved granular solids preheater.

The invention includes other objects and features of advantage, some of which, together with the foregoing, will appear hereinafter wherein the present preferred forms of apparatus and the preheater construction are disclosed.

In the drawings accompanying and forming a part hereof:

Figure l is a side elevation showing a typical installation embodying the present invention.

Figure 2 is a plan view of the apparatus shown in Figure 1.

Figure 3 is a side elevation of a preheater construction' of the present invention.

Figure 4 is an end View of the preheater shown in Figure 3.

Figure 5 is a sectional elevation taken along the lines 5-5 of Figure 3 and showing the construction of the preheater.

Figure 6 is a transverse section taken along the lines 66 of Figure 5'.

Figure? is a fragmentary View illustrating the preheater outlet and the feed to the kiln or furmice. 1 r

Figure 8 is a perspective view illustrating diagrammatically the flow of solids and gases through a preheater.

Referring particularly to Figures 1 and 2, I have shown a. typical granular solids heating operation including a kiln ll rotatably mounted upon rollers l2 in the usual manner. A burner 13 is provided at one end of the kiln to discharge products of combustion and a long flame into the kiln to calcine solid material in the kiln. The heated granular solids from the kiln pass through casing l4 into a rotary cooler l6. Air is admitted through end I! of the cooler to pass over the granular solids therein and then through casing [4 into the combustion zone and fire box around burner I3. The cool granular solids from the cooler discharge into a hopper 18 from which they are taken by a conveyor [9 and discharged into a silo 20 wherein the solids are stored prior to removal and utilization. At the other end of the kiln, the products of combustion are taken off tlu'cugh hood 23 and are introduced into a preheater generally indicated by 24 and which is further presently described in detail. Granular solids are fed into the upper end of preheater 24 by a. suitable feed conveyor mechanism generally indicated as 28. In the preheater, the granular solids fall downwardly counter-current in heat exchange relation with the products of combustion which finally issue from the preheater through line 21 and are forced out tl'n'ough a stack 28 under the draft provided by a blower 29.

Referring particularly to Figures 3 through 7, the preheater comprises a suitable structural framework indicated generally by SI and providing a vertically extending conduit or chute having an inlet opening 32 at its upper end and into which solids are discharged for heating. Positioned along each side of the casing 3! are a plurality of angularly positioned baflies 33 to direct material away from the sides of the casing.

Inverted V-shaped bafiies 34 are provided centrally of the casing to divide and to direct the flow of granular solids on to the next lower baffle 33. Material finally discharged off the lowermost inverted V-baflle 34 passes to a discharge opening defined by sides 36 and leading to a discharge conduit 31.

The products of combustion pass upwardly in heat exchange relation with the downward flow of solids. To eflect this, conduits 38, as and 40 are positioned at the ends of the casing 31.

These various conduits are connected by headers outside the casing 3| so that the heating fluid may be passed alternately back and forth through the casing in the passages provided by the baffles and the material to be heated. This relation is indicated best in Figure 8, which also shows a slightly different structural arrangement of baifles. The conduits mentioned are indicated by numerals 42, 43, 44 and 45. The products of combustion enter through pipe 4'! and pass transversely through the casing in heat exchange relation with the lowermost inverted V-baiile and the material on the sloping sides 36 (Figure 3), issuing on the other side of the casing into a header 48 which discharges the products of combustion into conduits or openings 42 and 42; the hot gases issuing from conduits 42 and 43, best shown in Figure 5, in heat exchange relation with material on lower baflle 34, are then collected and directed by header 49 into conduit 39, etc. Additional headers and 52 help to complete the passage for the heating fluid and finally the fluid passes through pipe bend 53 into the 4 uppermost conduit 4| and thence out through pipe 54 to the inlet of the exhaust blower or fan.

The angle of each baflie in the casing preferably approximates the angle of repose of the material so that the material tends to come to rest upon each bafiie and to reside thereon for a period of time suflicient to insure that the material can pick up heat from the bafiie, and constitute one wall of the conduit for the hot gases, the baffle constituting the other wall.

The heater is usually operated under such conditions that it is filled with the granular solids undergoing heating, as shown in Figure 8. Adjacent the discharge 3? (Figure 7) is provided a slidably movable transverse discharge feeder GI and comprising a. solid member extending across the discharge opening and adapted to be moved across the opening to shear oil a layer of heated material and advance this on to the discharge opening. To effect reciprocation, of the discharge member 6 l, a suitable reciprocating mechanism indicated generally by numeral 82 is provided. In this way, the flow of material through the preheater is carried on at a substantially uniform rate, but under such conditions that adequate residence time of the solid in the heater is insured.

Referring to Figure 8, I have indicated diagrammatically another form of preheater in which a plurality of lea-flies ll through T! are provided on opposite sides of the casing walls 18 and 19. The flow of the hot combustion gas is indicated by the line 8| having the several arrowheads thereon. The presence of the granular solids between the baflles and the course of flow of this is indicated by the shaded lines.

From the foregoing I believe it will be apparent that I have provided a relatively novel, improved system for the heating of granular solid materials as well as a novel and simplified and improved heater construction wherein the granular solids can be adequately preheated before being introduced into a kiln or other roasting or calcining furnace.

. In operation, the kiln is brought up to tempera ture in the usual manner, the products of combustion being passed through the preheater. When the kiln is nearly up to temperatiu'e, the feed of solids is commenced and the preheater is filled. By the time the kiln is up to temperature, the solids in the preheater will likewise be up to temperature and ready for discharge into the kiln. The feed to the preheater is coordinated with the kiln discharge, the preheater being maintained filled with the solids. The leaffles ensure thorough mixing of the solids in the preheater and their contact with the heated baf" fies, to the end that they are up to temperature when the solids issue and pass to the kiln.

I claim:

1. A heater for granular solids comprising a vertical shaft of rectangular horizontal section and having an inlet at its upper end and an outlet at its lower end; a series of horizontal bafiles positioned in said shaft and including a first baffle positioned centrally of said shaft and consisting of a pair of flat sheets extending downwardly in opposite direction from a common edge to discharge material from the inlet toward opposite sides of said shaft, a second baffle consisting of a pair of downwardly extending shelves each provided along a side of the shaft to receive material from the first baifle and with such shaft side to direct material toward the middle of the shaft, and a third bafiie positioned centrally of said shaft and consisting of a pair of flat sheets extending downwardly in opposite direction from a common edge to discharge material received from one of the shelves of the second ioaiile toward opposite sides of the shaft; a conduit connecting the underside of the third .loaffle to the underside of each shelf in the second baffie at one end thereof; a second conduit connecting the other end of each shelf in the second baffie to one end of the first bafiie on the underside thereof; and a third conduit connected to the underside of the first loafiie at the other end thereof.

2. A heater for granular solids comprising a vertical shaft of rectangular horizontal section and having an inlet at its upper end and an outlet at its lower end; a series of baffles :positioned horizontally in said shaft and including a first loafiie positioned centrally of said shaft and consisting of a pair of fiat sheets extending downwardly in opposite direction from a common edge to discharge material from the inlet toward opposite sides of said shaft, a second bafiie consisting of a pair of downwardly extending shelves each provided along a side of the shaft to receive material from the first baffie and with such shaft side to direct material toward the middle of the shaft, each shelf in the second baffle extending on each side of the plane of the first baflie discharging onto such shelf, and a third baffie positioned centrally of said shaft and consisting of a pair of flat sheets extending downwardly in opposite direction from a common edge to discharge material received from one of the shelves of the second baffle toward opposite sides of the shaft; a conduit connecting the underside of the third baffle to the underside of each shelf in the second baliie at one end thereof; a second conduit connecting the other end of each shelf in the second baffle to one end of the first 'loafiie on the underside thereof; and a third conduit connected to the underside of the first baffle at the other end thereof.

3. A heater for granular solids comprising a vertical shaft of rectangular horizontal section and having an inlet at its upper end and an outlet at its lower end; a series of horizontal baffles positioned in said shaft and including a first baffle positioned centrally of said shaft and consisting of a pair of fiat sheets extending downwardly in opposite direction from a common edge to discharge material from the inlet toward opposite sides of said shaft, a second baffle consisting of a pair of downwardly extending shelveseach provided along a side of the shaft at an elevation below that of the first loafile to receive material from the first haflie and with such shaft side to direct material toward the middle of the shaft, and a third hame positioned centrally of said shaft at an elevation below that of the second baflie and consisting of a pair of flat sheets extending downwardly in opposite direction from a common edge to discharge material received from one of the shelves of the second haffie toward opposite sides of the shaft, each of said loaflies (a) being positioned at substantially to and (b) extending above and below the projected plane of that hafiie which discharges material thereagainst; a conduit connecting the underside of the third baffle to the underside of each shelf in the second lloaifie at one end thereof; a second conduit connecting the other end of each shelf in the second baffle to one end of the first baffle on the underside thereof; and a third conduit connected to the underside of the first baflie at the other end thereof.

MARK LINTZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 159,014 Beach Jan. 26, 1875 363,865 Wales May 31, 1887 735,878 Hutton Aug. 11, 1903 1,299,791 Seaman Apr. 8, 1919 1,303,088 McCaig et a1. May 6, 1919 1,763,538 Randolph June 10, 1930 1,773,984 Foster Aug. 26, 1930 1,801,467 Uhle et a1. Apr. 21, 1931 2,202,498 Leaf May 28, 1940 2,451,024 Ellerbeck Oct. 21, 1948 FOREIGN PATENTS Number Country Date 425,316 Germany Feb. 18, 1926 

